A very mild access to 3,4-dihydroisoquinolines using triphenyl phosphite-bromine-mediated Bischler-Napieralski-type cyclization

Substituted β-phenylethylamides undergo smooth intramolecular cyclization to 3,4-dihydroisoquinolines in good to excellent yields when treated with bromotriphenoxyphosphonium bromide at –60 °C in dichloromethane in the presence of triethylamine. The reaction proceeds under the mildest conditions ever reported for Bischler–Napieralski-type cyclizations. When chlorotriphenoxyphosphonium choride is used, low yields are obtained instead